As next generation display devices to liquid crystal displays (LCDs), display devices with a display panel which has a two-dimensional array of light emitting device type luminous devices, such as an organic EL element (hereinafter called “organic EL element”), have been studied and developed recently (see Unexamined Japanese Patent Application KOKAI Publication No. H08-330600 (Patent Literature 1)).
An organic EL element includes an anode electrode, a cathode electrode, and an organic EL layer (luminous layer) which is formed between the pair of electrodes and has, for example, a luminous layer, a hole injection layer, etc. The organic EL element emits light based on energy generated by recombination of holes and electrons in the luminous layer.
A display device includes a plurality of n-channel FETs (Field Effect Transistors) for driving such organic EL elements.
Misalignment of the source electrode, the drain electrode, etc. may occur in such a transistor.
FIG. 13A and FIG. 13B are cross-sectional views showing the transistor. The transistor comprises a substrate 81, a gate electrode 82, a gate insulation film 83, an i-Si film 84, a BL (blocking layer) insulation film 85, an n+-Si film 86, a drain-side SD (Source/Drain) electrode 87d, a source-side SD electrode 87s, and an overcoat insulation film 88.
FIG. 13A shows a case where the SD electrodes 87d, 87s are laminated on the BL insulation film 85, around the gate electrode 82, disproportionally on the drain side. That is, FIG. 13A shows a case where Ls1<Ld1 (where Ls1 is the overlying length of the SD electrode 87s and the BL insulation film 85, and Ld1 is the overlying length of the SD electrode 87d and the BL insulation film 85).
FIG. 13B shows a case where the SD electrodes 87d, 87s are laminated on the BL insulation film 85, around the gate electrode 82, disproportionally on the source side. That is, FIG. 13B shows a case where Ls2>Ld2 (where Ls2 is the overlying length of the SD electrode 87s and the BL insulation film 85, and Ld2 is the overlying length of the SD electrode 87d and the BL insulation film 85).
When a source potential Vs=0 V is applied to the source electrode, a drain potential Vd=10 V is applied to the drain electrode, and a gate-source voltage Vg as shown in FIGS. 14A and 14B is applied to the gate electrode, the characteristic varies between the case shown in FIG. 13A and the case shown in FIG. 13B. Note that the scale of a drain current Id differs between FIG. 14A and FIG. 14B.
As shown in FIGS. 14A and 14B, the variation in characteristic particularly affects the ON current. A variation in ON current affects the amount of light from the organic EL element.